A conventional thermal transfer printer for a facsimile, a printing apparatus or the like using-ordinary paper as printing paper uses a heat-melting ink film.
FIG. 10 schematically illustrates a method for detecting an amount of ink film remaining in the conventional printer, and FIG. 11 and FIG. 12 schematically illustrate respective rotation speeds of an ink-film-winding shaft of the conventional printer.
As shown in FIG. 10, printing paper 1 undergoes printing using heat-melting ink film 2. The amount of ink film 2 remaining in printer 3 is detected based on the detected rotation speed of winding shaft 4.
Ink film 2 fed from supply shaft 5 passes between thermal transfer head 6 and platen roller 7 to be wound around take-up shaft 4 at a constant speed. Consequently, the rotation speed of winding shaft 4 is high when the amount of ink film 2 wound around winding shaft 4 is small as shown in FIG. 11, and is low when the amount of ink film 2 wound around winding shaft 4 is large as shown in FIG. 12.
In order to detect a variation in the above-described rotation speed, remaining-amount detector 9 detects the remaining amount of ink film 2. In remaining-amount detector 9, the rotation speed, which is detected by rotation-speed detector 8 disposed at winding shaft 4, is related with the remaining amount of ink film 2.
In conventional printer 3, when the rotation speed of winding shaft 4 is high as shown in FIG. 11, rotation-speed detector 8 can detect the rotation speed accurately. Accordingly, the remaining amount of ink film 2 can be detected accurately. When the rotation speed of winding shaft 4 is low as shown in FIG. 12, however, rotation-speed detector 8 cannot detect the rotation speed accurately. Thus, the remaining amount of ink film 2 is hardly detected accurately.
In other words, the amount of ink film 2 remaining sufficiently is detected accurately, although being allowed to be detected roughly. However, the remaining amount of ink film 2, upon being small cannot be detected accurately, although being to be detected accurately. Consequently, a warning for the remaining amount of ink film 2 must be given early for safety.